Effects of Fertilizers and Manures on Temporal Yield Variability of Winter Rye

The anticipated increases in environmental variability associated with climate change may lead to enhanced abiotic plant stresses (e.g. heat stress, drought stress, etc.) resulting in greater inter‐annual yield fluctuations and higher crop production risk. While there has been increasing attention to adaptation measures, there is little evidence available on how to change agronomic management strategies to maintain stable yields in winter rye production systems in Poland. This study uses rye yields from the unique Skierniewice Long‐term experiment (Poland) to examine for the first‐time the long‐term effects of different nutrient regimes on crop yield stability from 1966 to 2015. Yields from six combinations of mineral fertilizers and lime (CaNPK, NPK,CaPK, CaNK, CaNP, Ca), with and without additional manure, were used to estimate the temporal yield variability of winter rye. A novel statistical approach based on a mixed model approach with REML (restricted maximum likelihood) stability parameter estimation was used. The results showed that the use of additional manure in ‘sub‐optimal’ mineral fertilizer treatments, such as Ca and CaPK (without mineral N), reduced the temporal yield variability of rye. In contrast, additional organic input led to more variable rye yields in already ‘optimal’ treatments including mineral N (CaNPK and NPK), compared to those with no additional manure. Winter rye given CaNPK and NPK, without additional organic manure demonstrated high yield and low temporal yield variability. In contrast, yields of treatments with no mineral N (Ca and CaPK) and no additional manure supply were low and unstable. In addition, it was found that increasing soil organic carbon resulted in larger, more stable yields. These findings highlight the importance of ensuring rye crops receive sufficient fertilizer to maintain crop production levels and yield stability, especially in dry years. They also demonstrate the importance of avoiding the excessive use of organic manures when fertilizer inputs are sufficient to meet crop demand. Overall, the study provides novel insights about how to maintain grain yields and minimize temporal yield variation of rye in arable cropping systems, which will become increasingly important in a changing climate in Poland and in other temperate climate areas. This study also highlights the importance of soil organic carbon for improving the climate resilience of winter rye, while simultaneously meeting the demand for more sustainable management of the soil

Long-term trends in yield variance of temperate managed grassland

The management of climate-resilient grassland systems is important for stable livestock fodder production. In the face of climate change, maintaining productivity while minimizing yield variance of grassland systems is increasingly challenging. To achieve climate-resilient and stable productivity of grasslands, a better understanding of the climatic drivers of long-term trends in yield variance and its dependence on agronomic inputs is required. Based on the Park Grass Experiment at Rothamsted (UK), we report for the first time the long-term trends in yield variance of grassland (1965–2018) in plots given different fertilizer and lime applications, with contrasting productivity and plant species diversity. We implemented a statistical model that allowed yield variance to be determined independently of yield level. Environmental abiotic covariates were included in a novel criss-cross regression approach to determine climatic drivers of yield variance and its dependence on agronomic management. Our findings highlight that sufficient liming and moderate fertilization can reduce yield variance while maintaining productivity and limiting loss of plant species diversity. Plots receiving the highest rate of nitrogen fertilizer or farmyard manure had the highest yield but were also more responsive to environmental variability and had less plant species diversity. We identified the days of water stress from March to October and temperature from July to August as the two main climatic drivers, explaining approximately one-third of the observed yield variance. These drivers helped explain consistent unimodal trends in yield variance—with a peak in approximately 1995, after which variance declined. Here, for the first time, we provide a novel statistical framework and a unique long-term dataset for understanding the trends in yield variance of managed grassland. The application of the criss-cross regression approach in other long-term agro-ecological trials could help identify climatic drivers of production risk and to derive agronomic strategies for improving the climate resilience of cropping systems

The effects of cropping sequence, fertilization, and straw management on the yield stability of winter wheat (1986–2017) in the Broadbalk Wheat Experiment, Rothamsted, UK.

The development of resilient cropping systems with high yield stability is becoming increasingly important due to future climatic and agronomic challenges. Consequently, it is essential to be able to evaluate the effects of differing agronomic management practices, such as cropping sequences, and nutrient supply on the stability of crop yields. Long-term experiments are a valuable resource for investigating these effects, providing a sufficient number of years for accurate stability parameter estimation. The objective of the current study was to evaluate the effects of cropping sequence (#1: continuous vs rotational), fertilization (#2: mineral vs organic) and straw management in the case of continuous wheat (#3: removal vs incorporation) on the yield stability of winter wheat; yield risk (the probability of yield falling below a threshold yield level) and inter-annual yield variability were used as stability indicators of the effects. Long-term yield data from the Broadbalk Wheat Experiment (Rothamsted, United Kingdom) were analysed using a mixed model. Overall, the results showed that rotational cropping combined with supply of sufficient nutrients (N, P, and K) from mineral fertilizers, especially mineral N supply, ensured stable wheat yields whilst reducing the yield risk

Artifacts from manganese reduction in rock samples prepared by focused ion beam (FIB) slicing for X-ray microspectroscopy

The spatial distribution of transition metal valence states is of broad interest in the microanalysis of geological and environmental samples. An example is rock varnish, a natural manganese (Mn)-rich rock coating, whose genesis mechanism remains a subject of scientific debate. We conducted scanning transmission X-ray microscopy with near-edge X-ray absorption fine-structure spectroscopy (STXM-NEXAFS) measurements of the abundance and spatial distribution of different Mn oxidation states within the nano- to micrometer thick varnish crusts. Such microanalytical measurements of thin and hard rock crusts require sample preparation with minimal contamination risk. Focused ion beam (FIB) slicing was used to obtain ∼100–1000&thinsp;nm thin wedge-shaped slices of the samples for STXM, using standard parameters. However, while this preparation is suitable for investigating element distributions and structures in rock samples, we observed artifactual modifications of the Mn oxidation states at the surfaces of the FIB slices. Our results suggest that the preparation causes a reduction of Mn4+ to Mn2+. We draw attention to this issue, since FIB slicing, scanning electron microscopy (SEM) imaging, and other preparation and visualization techniques operating in the kilo-electron-volt range are well-established in geosciences, but researchers are often unaware of the potential for the reduction of Mn and possibly other elements in the samples.</p

Lengthening of maize maturity time is not a widespread climate change adaptation strategy in the US Midwest

Increasing temperatures in the US Midwest are projected to reduce maize yields because warmer temperatures hasten reproductive development and, as a result, shorten the grain fill period. However, there is widespread expectation that farmers will mitigate projected yield losses by planting longer season hybrids that lengthen the grain fill period. Here, we ask: (a) how current hybrid maturity length relates to thermal availability of the local climate, and (b) if farmers are shifting to longer season hybrids in response to a warming climate. To address these questions, we used county‐level Pioneer brand hybrid sales (Corteva Agriscience) across 17 years and 650 counties in 10 Midwest states (IA, IL, IN, MI, MN, MO, ND, OH, SD, and WI). Northern counties were shown to select hybrid maturities with growing degree day (GDD°C) requirements more closely related to the environmentally available GDD compared to central and southern counties. This measure, termed “thermal overlap,” ranged from complete 106% in northern counties to a mere 63% in southern counties. The relationship between thermal overlap and latitude was fit using split‐line regression and a breakpoint of 42.8°N was identified. Over the 17‐years, hybrid maturities shortened across the majority of the Midwest with only a minority of counties lengthening in select northern and southern areas. The annual change in maturity ranged from −5.4 to 4.1 GDD year−1 with a median of −0.9 GDD year−1. The shortening of hybrid maturity contrasts with widespread expectations of hybrid maturity aligning with magnitude of warming. Factors other than thermal availability appear to more strongly impact farmer decision‐making such as the benefit of shorter maturity hybrids on grain drying costs, direct delivery to ethanol biorefineries, field operability, labor constraints, and crop genetics availability. Prediction of hybrid choice under future climate scenarios must include climatic factors, physiological‐genetic attributes, socio‐economic, and operational constraints

Long-term analysis from a cropping system perspective - Yield stability, environmental adaptability, and production risk of winter barley

In the face of climate change, the potential impacts of adverse weather conditions on the productivity and vulnerability of cropping systems (CS) worldwide constitute a key agronomic issue upon which global food security depends. To date, little information regarding how the diversity of CS or agricultural practices affect the long-term yield responses of winter barley is available. The aim of this study was to investigate the impact of CS diversity in terms of cropping sequences, organic matter supplies, and nitrogen (N) fertilization on the yield vulnerability of winter barley. Yields were evaluated in terms of their stability, environmental adaptability, and production risk(probability of yield loss.Data from a 27-year experiment were statistically analysed using three mixed models giving residual maximum likelihood estimates including the Shukla stability variance index, the Finlay-Wilkinson environmental regression, and the Eskridge risk assessment approach. The results showed that winter barley grown in cropping sequences dominated by cereals had lower yield stability and environmental adaptability and greater production risks compared with winter barley grown in CS with higher crop diversity and additional organic matter inputs. When barley yields were compared at three doses of mineral N, the highest yield stability was achieved with the medium N dose (70kg N ha−1),followed by the higher level of N(140kgN ha−1). The most unstable yields with the highest production risks were observed when barley was grown without any mineral N fertilization. Overall, a higher level of crop diversity with organic matter inputs and intermediate N fertilization resulted in lower yield vulnerability in winter barley